Elwha River Dam Removal—Sediment Dispersal and Fish Relocations

Elwha Dam Removal

Many in the salmon restoration community share great joy and optimism that we will witness major dam removals in our lifetime. Each year the list of small and large dam removals grows and with it a hint of what large-scale restoration can look like. The Elwha Dam removal is the largest dam removal in the history of our country. Over 80,000 dams are relics to the hydroelectric age and have become silt traps.

The Elwha dam removal is a $351 million project that will occur in multiple stages and ultimately open up jish passage habitat for steelhead, Chinook, coho, sockeye, and pink salmon.

Removing the Elwha and Glines Canyon dams will free the Elwha River after nearly 100 years. Salmon populations will swell, from 3,000 to more than 300,000 as all jive species of Pacijic salmon return to more than 70 miles of river and stream.

The returning salmon and restored river will also help to renew the culture of the Lower Elwha Klallam Tribe, who have lived along the river since time immemorial. Tribal members will have access to sacred sites now inundated by water, and cultural traditions can be reborn.

by Jeff Duda, U.S. Geological Survey

Every year, Chinook salmon still come back to the pool below Elwha Dam, where they have been blocked from continuing their journey to spawning grounds upstream since construction began on the dam in 1910. Contractors are taking down Elwha and Glines Canyon dams in the largest dam-removal project ever. Photo: Steve Ringman / The Seattle Times.

After years of anticipation, volumes of Environmental Impact Statements, unprecedented mitigation projects, and the multifaceted collection of pre-dam removal data, the deconstruction phase of the Elwha River restoration project officially began this September. The removal of the 64 m Glines Canyon Dam and 33 m Elwha Dam represents one of the largest such projects of its kind in North America. The nearly 19 million m3 of sediment residing in the deltas and reservoirs will be eroded by the river in one of the largest releases of sediment into a river and marine waters in recorded history. The controlled release of sediment and the halting of dam notching and reservoir draw down during “fish windows” is largely determining a deconstruction schedule expected to last between 2 -3 years. High suspended sediment concentrations could last for up to 3-5 years following dam removal depending on weather conditions and river discharge. Anadromous fish, including three federally listed species (Puget Sound Chinook, steelhead, and bull trout), reside in the river downstream of Elwha dam for part of their life cycle. All five species of Pacific salmon and steelhead, which are either locally extirpated (sockeye) or persist in degraded spawning and rearing habitat, are expected to recolonize the watershed to degrees that will vary spatially and temporally due to life history characteristics and levels of human intervention. Because no fish passage structures were provided, naturally migrating salmon and their marine-derived nutrients have not seen the protected waters inside Olympic National Park since the Elwha dam was completed in 1913 at river kilometer 7.9. When passage is restored in 2014, salmon will have access to over 65 river kilometers of mainstem spawning and rearing habitat, at least as much floodplain channel habitat, and numerous tributaries, much of which occurs in wilderness.